1. Field of the Invention
The field of the invention relates to surgical instruments for fragmenting and removing tissue from the body, and particularly to the tip or needle portions of such instruments.
2. Brief Description of the Related Art
Instruments for fragmenting and removing tissue through the use of ultrasonic energy are well known in the field of eye surgery. Such instruments include hollow tips which are connected to ultrasonic transducers. The tips are caused to vibrate in a selected manner by the transducers.
The working tip of such a surgical instrument is also frequently connected to a vacuum source. When the tip is moved into engagement with tissue the surgeon wishes to fragment, ultrasonic vibrations are provided to the tip while the vacuum source is actuated. The resulting tissue fragments are accordingly aspirated through the tip. Fluid is provided to the surgical site in order to facilitate the aspiration of tissue fragments and to replace any body fluid which may be lost from the site.
Various working tips have been employed in surgical instruments for fragmenting and aspirating tissue fragments. U.S. Pat. No. 4,504,264 discloses a straight working tip, while U.S. Pat. No. 4,169,984 discloses two working tips, one straight and one curved. The tips disclosed in both patents are formed of thin, titanium tubes.
The working tips of some surgical instruments used in cataract surgery have outside diameters of about one millimeter and longitudinal bores of about 0.8 mm. The walls of such tips accordingly are about 0.1 mm in thickness. Bores of this size provide for the relatively efficient capturing of tissue fragments, but do not transfer ultrasonic energy as well as tips having thicker walls. They also tend to aspirate fluid at a higher rate than the surgeon may desire, making it more difficult to maintain proper pressure within the eye.
Working tips having 0.4 mm bores and wall having thicknesses of 0.3 mm have also been proposed for use in cataract surgery. The thicker walls theoretically provide for more efficient transmission of ultrasonic energy. However, the aspiration of tissue fragments is more difficult as larger fragments may be pushed away by the tip.
A working tip which is said to provide enhanced efficiency of fragmentation and aspiration is disclosed in U.S. Pat. No. 4,531,934. The patented tip is in the form of a needle having a gradually thinning wall between the end at which it is connected to a vibration concentrator and the opposite end through which tissue fragments enter the needle. The needle further includes an end wall which provides a sharp cutting edge where it adjoins the outer wall of the needle.